What Makes the World's Biggest Surfable Waves?
upstart writes in with an IRC submission:
What makes the world's biggest surfable waves?:
On Feb. 11, 2020, Brazilian Maya Gabeira surfed a wave off the coast of Nazare, Portugal, that was 73.5 feet tall. Not only was this the biggest wave ever surfed by a woman, but it also turned out to be the biggest wave surfed by anyone in the 2019-2020 winter surfing season-the first time a woman has ridden the biggest wave of the year.
As a female surfer myself-though of dubious abilities-this news made me really excited. I love it when female athletes accomplish things that typically garner headlines for men. But I am also a physical oceanographer and climate scientist at Brandeis University. Gabeira's feat got me thinking about the waves themselves in addition to the surfers who ride them.
[...] Just as light waves and sound waves will bend when they hit something or change speed-a process called refraction-so do ocean waves. When shallow bathymetry slows down a part of a wave, this causes the waves to refract. Similar to the way a magnifying glass can bend light to focus it into one bright spot, reefs, sand banks and canyons can focus wave energy toward a single point of the coast.
This is what happens at Nazare to create giant waves. Extending out to sea from the shore is an underwater canyon that was etched out by an ancient river when past sea level was much lower than it is today. As waves propagate toward shore over this canyon, it acts like a magnifying glass and refracts the waves toward the center of the canyon. This focusing of waves by the Nazare Canyon helps make the largest surfable waves on the planet.
YouTube video of Maya's record.
Journal References:
1.) Babanin, Alexander V., Rogers, W. Erick, de Camargo, Ricardo, et al. Waves and Swells in High Wind and Extreme Fetches, Measurements in the Southern Ocean, Frontiers in Marine Science (DOI: 10.3389/fmars.2019.00361)
2.) N. F. Barber and F. Ursell, The generation and propagation of ocean waves and swell. I. Wave periods and velocities, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences (DOI: 10.1098/rsta.1948.0005)
3.) L.S.Griffiths, R.Porter, Focusing of surface waves by variable bathymetry, Applied Ocean Research (DOI: 10.1016/j.apor.2011.08.004)
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